Circular and elliptical corrugated horns are known in the art. Circular corrugated horns provide an antenna with low side and back lobes, a rotationally symmetric radiation pattern and broad band performance. For example, U.S. Pat. No. 3,618,106 to Bryant teaches the use of a corrugated wave guide to form antenna feed horns. The corrugations extend throughout the length of the horn, and both the cross-sectional dimensions of the horn and the height of the corrugations are tapered to achieve broad bandwidth and good impedance match at each end of the horn. The exact guidelines for the relationship between flare angle and beamwidth are given in CLARRICOATS, P. J. B. & OLVER, A. D., Corrugated Horns for Microwave Antennas, (Peter Peregrinus, Ltd., 1984) and are incorporated by reference herein.
Elliptical corrugated wave guides are becoming increasingly popular to produce elliptically contoured beams with high polarization purity. However, elliptical corrugated horns are costly to manufacture because they are difficult to machine, and impractical to die cast as a single unit. This is primarily because the ridges are oriented at an angle with respect to the horn axis which makes die casting impractical.
A die-castable corrugated horn, with the ridges being oriented parallel to the horn axis, has previously been developed. However, in that construction, the corrugated horn is circular and only provides a circular beam. It is believed that no readily die-castable, elliptical, corrugated horn is commercially available and that the only available elliptical corrugated horns are costly to manufacture because of the orientation of the ridges relative to the horn axis.
The object of this invention is to provide a die-castable, or otherwise easily machined, corrugated horn that provides an elliptical beam for use with an elliptical antenna.
A further object of this invention is to provide a die-castable corrugated horn that provides non-circular and/or non-symmetrical beams for a variety of antenna applications.